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    <script>
        //柯里化思想

        //请实现以下效果
        function add(a, b, c, d) {
            return a + b + c + d
        }
        // console.log(add.length);
        //要求声明一个curry函数，函数add经过curry函数的处理后，每次调用只能接收一个参数
        const curry = (fn, arg) => {
            return function () {
                let args = [].slice.call(arguments);
                if (arg !== undefined) {
                    args = args.concat(arg)
                }
                if (args.length < fn.length) return curry(fn, args)

                return fn.apply(null, args);
            }
        }
        let addCurry = curry(add)
        const res2 = addCurry(1)(9)(3)(7) //6
        console.log(res2);
    </script>
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